Fungus resistant overcoating for color silver halide emulsion layers



Sept. ll, 1956 E s MACKEY 2,762,708

FUNGUS RESISTANT OVRCOATING FOR COLOR SILVER HALIOE EMULsION-LAYERS Filed om. 25, 1951 United States Patent() FUNGUS RESISTANT OVERCOATING FOR 'COLOR SILVER IMLIDE 'EMULSION LAYERS E. Scndder Mackey, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application October 23, 1951, Serial No. 252,809 Claims. (Cl. 95-8) This invention relates to color photography and particularly to the protection of color photographs against deterioration and destruction caused by mold and fungus growth.

Among the perils encountered in the processing and storing of colored photographic prints and films is the rapid growth of fungus, often referred to as mold or I mildew. The growth is especially noticeable on colored pictures in humid atmosphere that prevails in the tropical or sub-tropical zones, but is not confined to them and can also be observed, for instance, during the summer months in the moderate or temperate zones. Even under 2,762,708 Patented Sept. 11, 1956 wherein R and R1 represent hydrogen, an alkyl group,

carefully controlled storage conditions, fungus spores which are ever present in the air regardless of humidity and temperature, -settle on the emulsion surface and on the back layer of the color print or film. The spores may remain dormant so long as the humidity is low and grow rapidly as soon as the relative humidity exceeds 60 per cent. With its growth, the fungus produces both on exposed or unexposed color materials, a mos-sy or iilament pattern which has a detrimental effect on the final picture. Unexposed materials become desensitized and show discoloration, lose color density and have color stain in the white areas. Finished pictures which have been attacked by fungus growth are covered by an unsightly mossy-like surface coating. As a result, the film `or print loses its original pleasing appearance and eventually becomes a total loss. This discoloration makes the effects of fungus growth more apparent on color pictures than on black and white pictures which show only density changes.

The only remedies suggested by the art are the mechanical removal of the grown fungi with suitable cleaning solutions, and the protection of the pictures by mounting them between two gla-ss slides. Neither procedure is capable of restoring the attacked picture to its original beauty. Several chemical compounds have been proposed for the protection of organic matter against fungus growth but with limited success, especially when u-sed on black and white materials. All of the compounds, however, display some detrimental properties when used with color materials. Some cause fog, desensitization or both; others destroy or discolorize the dyes of the finished materials, while still others cause staining of the white areas of the finished pictures. Obviously, even one of these undesired properties will eliminate an otherwise effective fungicidal agent from its use in color photography.

An object of the present invention is to provide photoi. e., methyl, ethyl, propyl, isopropyl, butyl, etc., allyl, oxyalkyl or an alkoxyalkyl, i. e., allyloxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, etc., and Z represents the divalent methylene radicals necessary to complete a 5- or G-membered cycloaliphatic group such as cyclopentyl or cyclohexyl.

The following are examples of .suitable hydantoins characterized by the above formulae:

Hydantoin graphic color materials, unexposed as well as completely i' processed, which have an increased resistance to fungus growth.

It is another object `of the present invention to provide color materia-ls having resistance to mold and fungus growth without impairing their photographic properties. Other objects and advantages will appear hereinafter. I have discovered that the above objects are accomplished by providing a photographic element comprising a support and either at least one light sensitive silver S-methylhydantoin S-ethylhydantoin S-propylhydantoin 5,5-dimethylhydantoin 5,5 -diethylhydantoin 5,5-dicyclohexylhydantoin S-methyl-5isoproplhydantoin 5-ethyl-5-isobutylhydantoin S-methyl-S-ethylhydantoin 5 -methyl-S -isoamylhydantoin 5-methyl-S-ethoxyethylhydantoin 5( 1-sec.butoxyethyl -5-butylhydantain 5- 1-sec.butoxyethyl -S-ethylhydantoin 5- 1sec.butoxyethyl) -5-isoamylhydantoin 5( 1-sec.butoxyethyl -5-isobutylhydantoin 5- lsec.butoxyethyl -5-isopropylhydantoin 5( lsec.-butoxyethyl) -S-methylhydantoin 5( 1-sec.butoxyethyl) -S-propylhydantoin S-amyl-S- lsec.-butoxyethyl) hydantoin 5,5-bis (hexyloxymethyl) hydantoin 5,5-bis (isoamoxymethyl) hydantoin 5,5-bis (isobutoxymethyl)hydantoin 5,5-bis (methoxymethyDhydantoin 5,5 -bis (pnopoxymethyl) hydantoin 5,5 -bis allyloxymethyDhydantoin 5,5 -bis amoxymethyl) hydantoin 5,5 -bis sec.butoxymethyl) hydantoin 5,5 -bis ethoxymethyl) hydantoin S-allyl-S- (cyclohexenyl)hydantoin 5allyl5( l'-cyclohexenyl)hydantoin 5-methyl-5-cyclohexylhydantoin The following is merely a suggestive listin l g of the formaldehyde-hydantoin addition products which may be employed for the purpose herein set forth:

(1) CHIOH i't HaC/ \C=O 0== 11TH Resinous addition products of formaldehyde and hydantoins which are water-soluble, are readily prepared according to the process described in United States Patent 2,155,863 which discloses examples of such compounds contemplated herein.

By incorporating the hydantoin-formaldehyde addition products into the surface coating or super coat of an unexposed color material, the ability of the fungus to grow on the surface and within the photographic color material is substantially retarded and in most cases, completely inhibited for an indefinite period of time, especially under rigid testing conditions involving the storage of the unexposed material or the processed color picture in an atmosphere having relative humidity from 60 per cent to saturation at temperatures above 30 C. which are known to be conducive to the rapid growth of fungi. The exact mode of operation of the formaldehyde-hydantoin addition products is still unknown, but it is believed that they act as fungicidal agents without adversely affecting photographic qualities of the unexposed and undeveloped color materials or the finished dyes of the completely processed picture.

In the preparation of the surface coating for the silver halide emulsion, it is preferred to dissolve the addition product first in water or in aqueous alcohol and to incorporate the resulting solution into the dispersion or solution of a suitable colloidal carrier medium. However, the addition product per se may be dispersed in the solution of the colloidal carrier without dissolving it iirst in water or aqueous alcohol. The dispersion obtained by either method is applied in a known manner as a surface coating over the emulsion layer of a monolayer color material or the top layer of a multilayer color material. Despite the fact that the addition products are soluble in water, they are sufciently substantive to gelatin and other colloidal carriers and are not removed by the customary photographic processing solutions, thus insuring adequate protection of the color materials not only before but also after processing.

The addition products may be incorporated in gelatin or other colloidal materials such as organic esters of cellulose, polyamides, superpolyamides, polyesters, or synthetic resins such as vinyl acetal resins, partially hydrolyzed polyvinyl esters, polyvinyl alcohol mixed with resorcinol, polyvinyl propionaldehyde and the like. A surface active agent such as sulfated oleic acid, alkylated monosodium benzenesulfonate, dihexyl ester of sodium sulfosuccinate, sodium salt of an alkylnaphthalene sulfonic acid, sodium salt of tetrahydronaphthalene sulfonic acid, calcium glycerin phosphate, alkylphenylpolyethylene glycol, oleic acid ester of hydroxyethane sulfonic acid, and sulfonates of high molecular Weight primary or secondary aliphatic, aromatic and cycloaliphatic carboxy acids, may be added to effect a smoother coating. It is to be noted, however, that any commercially available surface active agent may be employed. The nature of the surface active agent is immaterial so long as it possesses wetting, spreading and preferably some dispersing and emulsifying properties, and its aqueous solutions are colorless or only slightly tinted. The colloids are applied in the form of solutions or dispersions in concentrations ranging from .5 to 5 per cent. Aqueous solutions or dispersions are preferred because of their ease of application.

The proportions of the addition products which may be incorporated into the surface coating or supercoat are not critical and the amounts employed will depend on the amount of material used and the iinal thickness of the surface coating. For practical purposes, I have found that the amounts of the formaldehyde-hydantoin addition product employed may range from .5 gram to 20 grams per liter of aqueous colloidal carrier dispersion. Inasmuch as one liter of a 2 per cent dispersion of gelatin in water will coat approximately square feet, it can be estimated that one square foot of overcoated color material will be covered by approximately 3 to 130 milligrams of the addition product. The actual concentration used will depend on the type of color material and varies also with the addition product employed. Depending on the color material, the most practical concentrations can be very readily determined by routine experiments.

Among the photographic multicolor materials which may be surface-coated with fungus growth inhibiting agents are color reversible ilm, color negative iilm, color positive iilm, color reversible white printing material coated on an opaque base, and color positive paper. ln these materials, the final dye images are produced with dye image intermediates such as colored or colorless color formers or bleachable azo dyes already present in the emulsion of the unexposed materials. However, dye images may be produced by the utilization of selective second exposure followed by development with developing solutions containing color formers and color developing agents as described in United States Patents 1,897,866; 1,900,870; 1,928,709 and 1,980,941.

A color reversible ilm containing color formers consists usually of layers integrally coated on the usual clear cellulose acetate or nitrate film base. Each of the emu. sions is sensitized to one of the primary colors of light, namely, blue, green and red. The top layer is blue sensitive. A filter layer, yellow in color and blue absorbing, lies under the top layer. Below this filter layer, lies a green sensitive emulsion layer and below this is a red sensitive emulsion layer. Each of the three silver halide emulsion layers contains dye forming components or color formers which unite during the development of a silver image in an aromatic amine developing agent to form a dye with the oxidation product of the developing agent.

The silver formed during development is removed after color development by treatment in an oxidizing bleach solution which dissolves silver directly or converts it into a `hypo soluble salt, followed by a treatment in a bath of sodium thiosulfate according to usual practice. A yellow dye is formed in the blue sensitive emulsion, a magenta dye in the green sensitive emulsion and a cyan dye in the red sensitive emulsion. Combinations of these three printing primaries will produce all of the other colors in the finished film or print. The color reversible white opaque material is prepared in the same manner as color reversible film and the color negative film with the exception that the base consists of an opaque white film. The color negative film is made up in the same manner as the color reversible film with the exception that it may contain a layer of clear gelatin between the red sensitive layer and the green sensitive layer. The color paper is also constructed in the same manner as the color reversible film and the color negative film with the exception that the emulsion is coated on a white paper base which may be subbed with a baryta coating. Suitable methods for the preparation of photographic multilayer materials have been described in the literature relating to color photography and are, therefore, vnot described herein.

The method of testing the formaldehyde-hydantoin addition products described in the following examples consisted of dividing a sheet of multicolor material into two equal areas and overcoating one of them with the protective surface coating containing the formaldehydehydantoin addition product and the other with a plain surface coating free from fungicidal agents. Either before or after processing, the protected and the unprotected materials were stored for extended periods of time in atmospheres having relative humidity between 60 per cent and saturation at temperatures between 30 and 35 C. Cultures of air borne fungi were obtained by the exposure of cultured media containing suitable nutrients for fungi to ordinary room air. These cultures were kept in the high humidity testing chambers in order to provide an ample supply of spores for the tests. t

The mold growth and its effects on the protected and unprotected color materials were recorded at regular intervals during the high humidity storage test.

The invention is further illustrated by the following self-explanatory drawing which shows in section, a multilayer material carrying on a base 11, a red sensitive silver halide layer 2 containing a cyan color former, a green sensitive silver halide emulsion layer 3 containing a magenta color former, a yellow filter layer 4, a blue sensitive silver halide emulsion layer 5 containing a yellow color former, and a protective surface coating 6 comprising a colloidal carrier and an addition product of formaldehyde and a hydantoin.

The following examples describe in detail, the methods for accomplishing the objects of this invention but it is to be understood that they are inserted only for the purpose of illustration.

Example I A multilayer color reversible duplicating material on a white opaque cellulose acetate film base prepared according to the methods described in United States Patents 2,179,228; 2,179,239; 2,186,849 and 2,220,187 was selected for this test. Each of the three integrally coated emulsion layers was sensitized to one of the primary colors of light, namely, blue, green and red. The top layer was blue sensitive and contained a color former for the yellow image. The middle layer was green sensitive and contained a color former for the magneta image and the bottom layer was red sensitive and contained a color former for the cyan image. A yellow filter layer separated the blue and green sensitive layers. Ten square feet of this material was divided into two equal sections. One of them was overcoated in total darkness with a surface layer obtained by dissolving 0.1 gram of monomethylol- 5,5dimethylhydantoin (prepared in a manner analogous to the procedure described in Annalen, vol. 365, p. 39, by heating together one molar equivalent of 5,5-dimethylhydantoin and 1.3 molar equivalents of 40 per cent aqueous formaldehyde solution) in 35 milliliters of 'a 2 per cent aqueous gelatin solution. The other section was surface coated with a plain 2 per cent aqueous gelatin solution. yBoth samples were allowed to dry, exposed to the same color transparency, and subsequently developed for 14 minutes at 68 F. in a developer of the following composition:

Grams 4-rnethylaminopheno1 sulfate 30 Sodium sulite l 50 Hydroquinone 6 Sodium carbonate 40 Sodium thiocyanate 2 Potassium bromide 2 a bath of the following composition:

Grams Acetic acid l0 Sodium acetate- 20 Water to make 1 liter.

Grams Sodium sulte 2.0 p-Aminodiethylaniline hydrochloride 4.0 Sodium carbonate (monohydrate) 67.5 Potassium bromide 1.0

The film was then short-stopped for 1 minute, hardened for 3 minutes,'washed in water for 5 minutes and bleached for 10 minutes in an aqueous solution containing 6 per cent of potassium ferricyanide, 1.5 per cent of potassium bromide, and 2 per cent of a sodium phosphate-sodium bisulfate buffer. The bleached film was Washed in water for 5 minutes, fixed for 5 nrinutes in a 20 per cent aqueous hypo solution, washed in running water for an additional 5 minutes and then dried.

Both prints, i. e., the one protected by the gelatin surface, coating containing the monomethylol5,5dimethyl hydantoin and the one which had been coated only with al plain gelatin surface layer were then transferred to a testing chamber, the` atmosphere of which was highly saturated with water vapors and kept at a temperature of 30 C. A culture of air borne fungi was kept in the testing chamber to provide an ample supply of spores. After one week, the type material which had been coated with only a plain gelatin surface layer was completely discolored and'covered with molds, while the sample protected by the surface coating containing the monomethylol-S,S-dmethyIhydantoin showed no indication of furligus lgrowth and had retained its original brilliant co ors.

Example II Example I was repeated with the exception that 0.1 gram of monomethylol-S,5-dimethylhydantoin was replaced by 0.2 gram of monomethylolhydantoin and that the two samples were subjected to the high humidity fungus growth test before exposure and processing. The type which contained no protective agent in the surface coating was completely covered with mold after two weeks, whereas the sample which had been surface coated with a gelatin solution containing monomethylolhydanton appeared free from mold growth. When the high humidity storage test was repeated in total darkness and the two samples subsequently exposed and processed as described in Example I, it was observed that the picture obtained on the material was locally desensitized and streaky, showing the effects of fungus growth whereas the sample protected by the surface coating containing the 7 monomethylolhydantoin was equal in pictorial quality to one obtained on a control material which had not been subjected to the severe test conditions.

Example III Example I was repeated with the exception that 0.1 gram of monomethylol-S,5-dimethylhydantoin was replaced by 0.4 gram of a 5,5-dirnethylhydantoin-formaldehyde resin prepared as described in Example I of United States Patent 2,155,863. Both samples, i. e., the type covered with a plain gelatin surface coating and the material protected by the surface layer containing the 5,5- dimethylhydautom-formaldehyde resin were exposed and processed as in Example I and then subjected to the high humidity fungus test. After one week, the type was badly discolorized and covered with mold growth whereas the sample protected by the 5,5-dimethylhydantoin formaldehyde resin was free from mold and showed no discoloration.

Correspondingly efficient protection against fungus growth was observed when the treating steps of Examples I to III were applied to negative and positive lm and color positive paper.

It will be obvious from the foregoing examples that the invention is not restricted to one type of color photographic material but is also useful when employed with other multior mono-layer color materials which yield multicolor pictures such as, for example, multicolor photographic materials which are color developed by azine developers, i. e., aromatic triamines to yield azine (phenazoniurn) dye images as described in United States Patent 2,486,440; multicolor photographic materials in which the lina'l dye images are azo dye images prepared according to the procedural steps disclosed in United States Patents 1,985,344 and 2,020,775; multicolor photographic materials free from color formers in which the final dye images are formed by the use of selective second exposure, and color formers containing developers as describedl in United States Patents 1,897,866; 1,900,870; 1,928,709 and 1,980,941', multicolor materials utilizing mixed grain emulsions and having less than three superposed emulsion layers as exemplified by the single layer material described in United States Patent 2,548,526, and the double layer material described in United States Patent 2,490,751. n

Accordingly, various modifications of this invention will occur to persons skilled in the art and it is, therefore, understood that the patent granted shall only be limited by the appended claims.

I claim:

l. A photographic element comprising a support and at least one light sensitive silver halide emulsion layer containing at least one dye image intermediate selected from the group consisting of colorless and colored color formers reactable with the oxidation products of an aromatic amine developer to form a dye image, the uppermost layer of said element being provided with a colloidal surface coating comprising a colloidal carrier material having dispersed therein in a fungus growth inhibiting amount, an addition product of formaldehyde and a compound selected from the class consisting of those having the following formulae:

and

wherein R and R1 represent a member selected from the class consisting of hydrogen, alkyl, allyl, oxyalkyl and alkoxyalkyl groups and Z represents the divalent methylene radicals necessary to complete a member selected from the class consisting of 5- and -membered cycloaliphatic groups, said fungus growth inhibiting amount being on the order of from 3 to 130 milligrams of addition product per square foot of overcoated lm, and from 0.5 to 20 grams of addition product per from 5 to 50 grams of colloidal carrier material.

2. A photographic element according to claim 1 wherein the addition product is monomethylol-S,5-dimethylhydantoin.

3. A photographic element according to claim l wherein the addition product is monomethylol-S-methylhydantoin.

4. A photographic element according to claim 1 wherein the addition product is monomethylolhydantoin.

5. A photographic element according to claim 1 wherein the addition product is the water-soluble, resinous condensation product of formaldehyde and 5,5-dimethylhydantoin.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Dimethyl I-Iydantoin-Formaldehyde Resin, Du Pont advertisement, page 3243, Chem. and Eng. News, November 3, 1947. 

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND AT LEAST ONE LIGHT SENSITIVE SILVER HALIDE EMULSION LAYER CONTAINING AT LEAST ONE DYE IMAGE INTERMEDIATE SELECTED FROM THE GROUP CONSISTING OF COLORLESS AND COLORED COLOR FORMERS REACTABLE WITH THE OXIDATION PRODUCTS OF AN AROMATIC AMINE DEVELOPER TO FORM A DYE IMAGE, THE UPPERMOST LAYER OF SAID ELEMENT BEING PROVIDED WITH A COLLOIDAL SURFACE COATING COMPRISING A COLLOIDAL CARRIER MATERIAL HAVING DISPERSED THEREIN IN A FUNGUS GROWTH INHIBITING AMOUNT, AN ADDITION PRODUCT OF FORMALDEHYDE AND A COMPOUND SELECTED FROM THE THE CLASS CONSISTING OF THOSE HAVING THE FOLLOWING FORMULAE: 